Inkjet head and inkjet recording apparatus

ABSTRACT

According to an embodiment, an inkjet head includes a pressure cell structure. The pressure cell structure includes pressure cells, flow control paths, and slits. The flow control paths are formed on both the sides of the pressure cells, and control flow of ink flowing into the pressure cells. The slits are in communication with the pressure cells and the flow control paths. The width of the slit is smaller than the width of the pressure cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2015-059672, filed on Mar. 23,2015, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described here generally relate to an inkjet head and aninkjet recording apparatus.

BACKGROUND

For example, an on-demand inkjet head ejects ink drops toward recordingpaper, and an image is thereby formed on the recording paper. Such kindof inkjet head includes nozzles and actuators corresponding to eachother one to one.

Piezoelectric actuators are formed on the surface of a substrate, andnozzle holes are formed corresponding to the actuators. Further,pressure cells are formed in the substrate corresponding to theactuators, the pressure cell starting from the back surface of thesubstrate and ending at the actuator. Further, ink is introduced fromthe back surface of the substrate and filled in the pressure cells, theactuators pressurize the ink filled in the pressure cells, and theinkjet head ejects the ink from the nozzle holes.

In the inkjet head, when printing, air bubbles may enter the pressurecells from the nozzles and the ink supply paths. In this case, theactuators cannot pressurize the ink, and the ink is ejected poorly. Inorder to recover from such poor ink ejection, it is necessary to stopprinting, and to suck out the ink from the nozzles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view schematically showing an inkjetrecording apparatus of a first embodiment.

FIG. 2 is a diagram schematically showing the structure of an ink-supplysystem of an inkjet printer of the first embodiment.

FIG. 3 is a plan view showing how pressure cells are formed and arrangedon the substrate of the inkjet head of the first embodiment.

FIG. 4 is a longitudinal sectional view showing the main part of thecross sectional structure around one nozzle of the inkjet head.

FIG. 5 is a cross sectional view showing the main part of the ink supplymember of the inkjet head of the first embodiment.

FIG. 6 is a cross sectional view in the F6-F6 line of FIG. 4.

FIG. 7 is a plan view showing how pressure cells are formed and arrangedon the substrate of the inkjet head of a second embodiment.

DETAILED DESCRIPTION

According to one embodiment, an inkjet head includes a pressure cellstructure, a nozzle plate, and an ink flow path structure. The pressurecell structure includes pressure cells that retain ink, each of thepressure cells being formed in a thickness direction of the pressurecell structure from one end surface to the other end surface. Thepressure cell structure further includes flow control paths that controlflow of the ink flowing into the pressure cells, the flow control pathsbeing formed at both the sides of the pressure cells, the pressure cellsbeing interposed between the flow control paths, each of the flowcontrol paths being formed in the thickness direction of the pressurecell structure from the one end surface of the pressure cell structureto the other end surface. The pressure cell structure further includesslits, each of the slits being in communication with each of thepressure cells and each of the flow control paths, each of the slitshaving a width smaller than a width of each of the pressure cells. Thenozzle plate includes actuators formed on the one end surface of thepressure cell structure, each of the actuators covering each of thepressure cells, the actuators deforming in the thickness direction ofthe pressure cell structure depending on a drive voltage. The nozzleplate further includes nozzles, each of the nozzles being formedcorresponding to each of the actuators, each of the nozzles being incommunication with each of the pressure cells, each of the nozzlesejecting the ink retained in each of the pressure cells. The ink flowpath structure is bonded to the other end surface of the pressure cellstructure. The ink flow path structure includes ink flow paths incommunication with each of the pressure cells via each of the flowcontrol paths and each of the slits.

Hereinafter, embodiments will be described with reference to thedrawings. In the drawings, the same reference symbols show the same orsimilar parts.

First Embodiment

FIG. 1 to FIG. 6 show a first embodiment. Note that each element, whichcan be expressed by some terms, may sometimes be expressed by anotherterm or other terms. However, it does not mean that any element, whichis only expressed by a single term, is never expressed by another termor other terms. In addition, it does not mean that another term or otherterms, which is/are not exemplified, is/are never used to express eachelement.

FIG. 1 is a cross sectional view showing the inkjet printer 1 of thefirst embodiment. The inkjet printer 1 is an example of an inkjetrecording apparatus. Note that an inkjet recording apparatus may beanother apparatus such as a copy machine instead of the inkjet printer.

As shown in FIG. 1, the inkjet printer 1 conveys recording paper P, forexample, as a recording medium, and at the same time, performs variousprocesses such as image forming. The inkjet printer 1 includes thehousing 10, the paper cassette 11, the copy receiving tray 12, theholding roller (drum) 13, the conveyer apparatus 14, the holdingapparatus 15, the image forming apparatus 16, the static-eliminating andpeeling apparatus 17, the inversing apparatus 18, and the cleaningapparatus 19.

The paper cassette 11 stores a plurality of sheets of recording paper P,and arranged in the housing 10. The copy receiving tray 12 is arrangedat the top of the housing 10. The inkjet printer 1 forms an image onrecording paper P, and discharges the recording paper P to the copyreceiving tray 12.

The conveyer apparatus 14 includes guides and conveyer rollers arrangedalong the path on which the recording paper P is conveyed. The conveyerroller is driven by a motor, rotates, and thus conveys the recordingpaper P from the paper cassette 11 to the copy receiving tray 12.

The holding roller 13 includes a cylindrical frame made of a conductor,and a thin insulation layer formed on the surface of the frame. Theframe is grounded. The holding roller 13 rotates where it holds therecording paper P on its surface, and thus conveys the recording paperP.

The holding apparatus 15 presses the recording paper P, which isdischarged from the paper cassette 11 by the conveyer apparatus 14, onthe surface (outer surface) of the holding roller 13. The holdingapparatus 15 presses the recording paper P on the holding roller 13, andthen attaches the recording paper P to the holding roller 13 by anelectrostatic force of the electrostatically-charged recording paper P.The holding roller 13 holds the recording paper P where the recordingpaper P is attached to the holding roller 13. The holding roller 13rotates, and thereby conveys the held recording paper P.

The image forming apparatus 16 forms an image on the recording paper Pon the outer surface of the holding roller 13, the recording paper Pbeing held by the holding apparatus 15. The image forming apparatus 16includes the inkjet heads 21, which face the surface of the holdingroller 13. The inkjet heads 21 eject four-color inks (for example, cyan,magenta, yellow, and black) toward the recording paper P, and therebyform an image on the recording paper P.

The static-eliminating and peeling apparatus 17 eliminates staticelectricity from the recording paper P, on which the image is formed,and thereby peels the recording paper P from the holding roller 13.Specifically, the static-eliminating and peeling apparatus 17electrically charges the recording paper P, and thereby eliminatesstatic electricity from the recording paper P. Further, thestatic-eliminating and peeling apparatus 17 includes a peeling nail (notshown), and inserts the peeling nail between the static-eliminatedrecording paper P and the holding roller 13. As a result, the recordingpaper P is peeled from the holding roller 13. The conveyer apparatus 14conveys the recording paper P, which is peeled from the holding roller13, to the copy receiving tray 12 or the inversing apparatus 18.

The cleaning apparatus 19 cleans the holding roller 13. The cleaningapparatus 19 is arranged at the downstream of the static-eliminating andpeeling apparatus 17 in the rotational direction of the holding roller13. The cleaning apparatus 19 includes the cleaning member 19 a. Thecleaning apparatus 19 causes the cleaning member 19 a to come into closecontact with the surface of the rotating holding roller 13, and therebycleans the surface of the rotating holding roller 13.

In order to form images on the two sides of the recording paper P, theinversing apparatus 18 turns the recording paper P, which is peeled fromthe holding roller 13, upside down, and supplies the recording paper Pto the surface of the holding roller 13 again. Specifically, theconveyer apparatus 14 switches back the peeled recording paper P theother way around, and thereby conveys the recording paper P to theinversing apparatus 18. The inversing apparatus 18 includes apredetermined inversion path. The inversing apparatus 18 conveys therecording paper P along the inversion path, and thereby turns therecording paper P upside down.

FIG. 2 shows an ink-supply system of the inkjet printer 1. The inkjetprinter 1 includes the ink tanks 501, 502, the pressure control pumps503, 504, and the ink circulation pump 505, which are connected to eachof the inkjet heads 21. Each inkjet head 21 is connected to the inktanks 501, 502, which store ink of the corresponding color. The inkjethead 21 includes an ink inlet port (not shown) and an ink outlet port(not shown). The ink inlet port is connected to the ink tank 501, andthe ink outlet port is connected to the other ink tank 502. Further, theink tank 501, which is connected to the ink inlet port, is connected tothe ink tank 502, which is connected to the ink outlet port, via the inkcirculation pump 505. Thanks to this structure, the ink circulation pump505 causes the ink in the ink tank 502, which is at the ink outlet portside, to flow into the ink tank 501, which is at the ink inlet portside.

Hereinafter, with reference to FIG. 3 and FIG. 4, the internal structureof one ink circulation-type inkjet head 21 of the image formingapparatus 16 will be described schematically. FIG. 3 is a plan viewshowing how pressure cells are formed and arranged on the substrate ofthe inkjet head 21. FIG. 4 is a longitudinal sectional view showing themain part of the cross sectional structure around one nozzle of theinkjet head 21. Note that, for illustrative purposes, FIGS. 3 and 4 showvarious elements, which are actually hidden, in solid lines. Inaddition, FIGS. 3 and 4 show the inkjet head 21 of this embodimentschematically. The sizes shown in FIGS. 3 and 4 may sometimes bedifferent from those described in this embodiment.

The inkjet head 21 ejects ink drops toward the recording paper P held bythe holding roller 13, and thereby forms texts and images thereon. Asshown in FIG. 4, the inkjet head 21 includes the nozzle plate 100, thepressure cell structure 200, and the ink flow path structure 300. Thepressure cell structure 200 is an example of the substrate.

The nozzle plate 100 has a rectangular plate shape. The nozzle plate 100is formed on the pressure cell structure 200, the nozzle plate 100 andthe pressure cell structure 200 being an assembly. The nozzle plate 100includes the nozzles (orifices, ink ejecting holes) 101 and theactuators 102.

The nozzles 101 are circular holes. The diameter of the nozzle 101 is,for example, 20 μm. As shown in FIG. 3, the nozzles 101 are arrayed inthe longer-side direction (horizontal direction of FIG. 3) and theshorter-side direction (vertical direction of FIG. 3) of the nozzleplate 100. In other words, the nozzles 101 are arranged in matrix. Thenozzles 101 are arranged such that the nozzles 101 in one line arespaced apart from the nozzles 101 in the next line in the longer-sidedirection of the nozzle plate 100. According to this structure, theactuators 102 are arranged in a higher density.

The distance between the center of one nozzle 101 and the center of thenext nozzle 101, the nozzles 101 being adjacent to each other in thelonger-side direction of the nozzle plate 100, is 340 μm, for example.The distance between the center of one line of the nozzles 101 and thecenter of the next line of the nozzles 101, the lines being adjacent toeach other in the shorter-side direction of the nozzle plate 100, is 240μm, for example.

The actuators 102 are arranged corresponding to the nozzles 101 one toone. As shown in FIG. 3, the actuator 102 and the corresponding nozzle101 are arranged coaxially. The actuator 102 has an annular shape, andsurrounds the corresponding nozzle 101. Alternatively, the actuator 102may have a semi-open annular shape (C shape), for example.

The pressure cell structure 200 is made of a silicon wafer, and has arectangular plate shape. Alternatively, the pressure cell structure 200may be another semiconductor such as a silicon carbide (SiC) substrateand a germanium substrate, for example. Alternatively, the substrate(the pressure cell structure 200) may be made of another material suchas ceramics, glass, quartz, resin, and metal. Ceramics such as, forexample, nitride, carbide, and oxide such as alumina ceramics, zirconia,silicon carbide, silicon nitride, and barium titanate is used. Resinsuch as, for example, a plastic material such as ABS (acrylonitrilebutadiene styrene), polyacetal, polyamide, polycarbonate, andpolyethersulfone is used. Metal such as, for example, aluminum andtitanium is used. The thickness of the pressure cell structure 200 is,for example, 725 μm. The thickness of the pressure cell structure 200 ispreferably, for example, in the range of 100 to 775 μm.

As shown in FIG. 4, the pressure cell structure 200 includes the firstend surface 200 a, the second end surface 200 b, and the pressure cells(ink cells) 201. The first and second end surfaces 200 a, 200 b areflat. The second end surface 200 b is opposite to the first end surface200 a. The nozzle plate 100 is fixed to the first end surface 200 a.

The pressure cells 201 are circular holes. The diameter of the pressurecell 201 is, for example, 190 μm. Note that the shape of the pressurecell 201 is not limited to this. The pressure cell 201 penetratesthrough the pressure cell structure 200 in its thickness direction, andhas an opening through the first end surface 200 a and an openingthrough the second end surface 200 b. The nozzle plate 100 covers thepressure cells 201 having the openings through the first end surface 200a.

The pressure cells 201 are arranged corresponding to the nozzles 101 oneto one. In other words, the pressure cell 201 and the correspondingnozzle 101 are arranged coaxially. According to this structure, thepressure cell 201 is in communication with the corresponding nozzle 101.The pressure cell 201 is in communication with the outside of the inkjethead 21 via the nozzle 101.

Next, the nozzle plate 100 will be described.

As shown in FIG. 3 and FIG. 4, the nozzle plate 100 includes theabove-mentioned nozzles 101 and actuators 102, the shared electrode 106,the wiring electrodes 108, the vibration plate 109, the protective film(insulation film) 113, and the ink-repellent film 116. The sharedelectrode 106 is an example of a first electrode (common electrode). Thewiring electrode 108 is an example of a second electrode (individualelectrode). The nozzle 101 penetrates through the vibration plate 109and the protective film 113, the vibration plate 109 being layered onthe first end surface 200 a of the pressure cell structure 200, theprotective film 113 being layered on the vibration plate 109.

The vibration plate 109 is formed on the first end surface 200 a of thepressure cell structure 200, and has a rectangular plate shape. Thethickness of the vibration plate 109 is, for example, 2 μm. Preferably,the thickness of the vibration plate 109 is in the range of 1 μm to 50μm, approximately. The protective film 113 is an example of aninsulator.

The vibration plate 109 is, for example, an SiO₂ (silicon dioxide) filmformed on the first end surface 200 a of the pressure cell structure200, and has a rectangular plate shape. In other words, the vibrationplate 109 is an oxide film of the pressure cell structure 200, which isa silicon wafer. The vibration plate 109 may be made of another materialsuch as single-crystal Si (silicon), Al₂O₃ (aluminum oxide), HfO₂(hafnium oxide), ZrO₂ (zirconium oxide), and DLC (Diamond Like Carbon).

The vibration plate 109 includes the first surface 109 a and the secondsurface 109 b. The first surface 109 a is fixed to the first end surface200 a of the pressure cell structure 200, and covers the pressure cell201. The second surface 109 b is opposite to the first surface 109 a.The actuator 102, the shared electrode 106, and the wiring electrode 108are arranged on the second surface 109 b of the vibration plate 109.

As shown in FIG. 4, each actuator 102 includes the piezoelectric film111, the electrode part 106 a of the shared electrode 106, the electrodepart 108 a of the wiring electrode 108, and the insulation film 112. Thepiezoelectric film 111 is an example of a piezoelectric member.

The piezoelectric film 111 is a film made of lead zirconium titanate(PZT). Alternatively, the piezoelectric film 111 may be made of any oneof various materials such as, for example, PTO (PbTiO₃: lead titanate),PMNT (Pb(Mg_(1/3)Nb_(2/3))O₃—PbTiO₃), PZNT(Pb(Zn_(1/3)Nb_(2/3))O₃—PbTiO₃), ZnO, and AlN.

The piezoelectric film 111 has an annular shape. The piezoelectric film111 is arranged coaxially with the nozzle 101 and the pressure cell 201.The piezoelectric film 111 surrounds the nozzle 101. The outer diameterof the piezoelectric film 111 is, for example, 144 μm. The innerdiameter of the piezoelectric film 111 is, for example, 30 μm.

The thickness of the piezoelectric film 111 is, for example, 2 μm. Thethickness of the piezoelectric film 111 is determined based on itspiezoelectric property, dielectric breakdown voltage, and the like. Thethickness of the piezoelectric film 111 is preferably in the range of0.1 μm to 5 μm, approximately.

The piezoelectric film 111 is arranged between the electrode part 108 aof the wiring electrode 108 and the electrode part 106 a of the sharedelectrode 106. In other words, the electrode part 108 a of the wiringelectrode 108 is formed on one side of the piezoelectric film 111, andthe electrode part 106 a of the shared electrode 106 is formed on theother side of the piezoelectric film 111.

The piezoelectric film 111 is polarized in the thickness direction (Zdirection) at the time when the film is formed. In other words, forexample, the piezoelectric film 111 is polarized, the side on theelectrode part 106 a being positive, the side of the piezoelectric film111 on the electrode part 108 a being negative.

Drive voltage is applied to the electrode parts 106 a, 108 a of theshared electrode 106 and the wiring electrodes 108. When the drivevoltage is applied, the electric field in the thickness direction (Zdirection) of the piezoelectric film 111 is applied to the polarizedpiezoelectric film 111. At this time, the piezoelectric film 111 expandsor contracts in the electric field direction (Z direction), andcontracts or expands in the direction (X, Y directions) perpendicular tothe electric field direction, at the same time. As a result, theactuator 102, which includes the piezoelectric film 111, expands orcontracts in the electric field direction (Z direction) and contracts orexpands in the direction (X, Y directions) perpendicular to the electricfield direction, at the same time. When the actuators 102 expands andcontracts, the vibration plate 109 deforms in the thickness direction (Zdirection) of the nozzle plate 100. As a result, the pressure of the inkin the pressure cell 201 is changed.

The electrode part 108 a of the wiring electrode 108 is one of the twoelectrodes connected to the piezoelectric film 111. The electrode part108 a of the wiring electrode 108 has an annular shape larger than thepiezoelectric film 111, and is at the ejection side (external side ofthe inkjet head 21) of the piezoelectric film 111. The outer diameter ofthe electrode part 108 a is, for example, 148 μm. The inner diameter ofthe electrode part 108 a is, for example, 26 μm. In other words, theinner peripheral part of the electrode part 108 a is apart from thenozzle 101.

The electrode part 106 a of the shared electrode 106 is the other of thetwo electrodes connected to the piezoelectric film 111. The electrodepart 106 a of the shared electrode 106 has an annular shape smaller thanthe piezoelectric film 111, and is arranged on the second surface 109 bof the vibration plate 109. The outer diameter of the electrode part 106a is, for example, 140 μm. The inner diameter of the electrode part 106a is, for example, 34 μm.

The insulation film 112 is outside of the area in which thepiezoelectric film 111 is formed, and is interposed between the sharedelectrode 106 and the wiring electrode 108. In other words, the sharedelectrode 106 is separated from the wiring electrode 108, thepiezoelectric film 111 or the insulation film 112 being interposedtherebetween. The insulation film 112 is made of, for example, SiO₂. Theinsulation film 112 may be made of another insulation material. Thethickness of the insulation film 112 is, for example, 0.2 μm.

A wiring electrode terminal unit (not shown) is arranged at the end ofthe wiring electrode 108. The wiring electrode terminal unit isconnected to a controller (not shown) via a flexible cable, for example,and transmits signals output from the controller to drive the actuator102.

A shared electrode terminal unit (not shown) is arranged on the secondsurface 109 b of the vibration plate 109. The shared electrode terminalunit is at the end of the shared electrode 106, and is connected to GND(grounded=0 V), for example.

The wiring electrode 108 is connected to the piezoelectric film 111 ofthe corresponding actuator 102 one to one, and transmits signals todrive the actuator 102. The wiring electrode 108 is an individualelectrode that drives the piezoelectric film 111 independently. Each ofthe wiring electrodes 108 includes the electrode part 108 a, a wiringpart, and the wiring electrode terminal unit.

The wiring part of the wiring electrode 108 extends from the electrodepart 108 a to the wiring electrode terminal unit. The electrode part 108a of the wiring electrode 108 and the nozzle 101 are arranged coaxially.The inner peripheral part of the electrode part 108 a is slightly apartfrom the nozzle 101.

The wiring electrodes 108 are thin films made of Pt (platinum). Notethat the wiring electrodes 108 may be made of another material such asNi (nickel), Cu (copper), Al (aluminum), Ag (silver), Ti (titanium), W(tantalum), Mo (molybdenum), and Au (gold). The thickness of the wiringelectrode 108 is, for example, 0.5 μm. Preferably, the film thickness ofthe wiring electrodes 108 is from 0.01 μm to 1 μm, approximately.

The shared electrode 106 is connected to the piezoelectric films 111.The shared electrode 106 includes the electrode parts 106 a, wiringparts, and two shared electrode terminal units. The wiring parts of theshared electrode 106 extend from the electrode parts 106 a to theopposite sides of the wiring parts of the wiring electrodes 108. Thewiring parts of the shared electrode 106 join together at the end of thenozzle plate 100 in the Y direction, and extend along both the edges ofthe nozzle plate 100 in the X direction. The electrode part 106 a andthe nozzle 101 are arranged coaxially. The shared electrode terminalunits are arranged at both the edges of the nozzle plate 100 in the Xdirection.

The shared electrode 106 is made of a Pt (platinum)/Ti (titanium) thinfilm. The shared electrode 106 may be made of another material such asNi, Cu, Al, Ti, W, Mo, and Au. The thickness of the shared electrode 106is, for example, 0.5 μm. The thickness of the shared electrode 106 isapproximately 0.01 to 1 μm, preferably.

The width of the wiring part of the wiring electrode 108 is 80 μm, andthe width of the wiring part of the shared electrode 106 is 80 μm, forexample. The wiring parts of some of the wiring electrodes 108 passthrough two adjacent actuators 102.

As shown in FIG. 4, the protective film 113 is arranged on the secondsurface 109 b of the vibration plate 109. The protective film 113 ismade of, for example, insulating polyimide. Alternatively, theprotective film 113 may be made of another material such as resin,ceramics, and metal (alloy). Resin such as, for example, a plasticmaterial such as ABS (acrylonitrile butadiene styrene), polyacetal,polyamide, polycarbonate, and polyethersulfone is used. Ceramics suchas, for example, nitride, carbide, and oxide such as zirconia, siliconcarbide, silicon nitride, and barium titanate is used. Metal such as,for example, aluminum, SUS, and titanium is used.

The Young's modulus of the material of the protective film 113 islargely different from the Young's modulus of the material of thevibration plate 109. The deformation amount of a member having a plateshape is affected by the Young's modulus of the material and thethickness of the plate. The smaller the Young's modulus and the smallerthe thickness of a plate, the larger the deformation amount of the platewhen a force is applied constantly. The vibration plate 109 is made ofSiO₂, the Young's modulus thereof being 80.6 GPa. The protective film113 is made of polyimide, the Young's modulus thereof being 4 GPa. Thedifference between the Young's modulus of the vibration plate 109 andthe Young's modulus of the protective film 113 is 76.6 GPa.

The thickness of the protective film 113 is, for example, 4 μm.Preferably, the thickness of the protective film 113 is approximately inthe range of 1 μm to 50 μm. The protective film 113 covers the secondsurface 109 b of the vibration plate 109, the shared electrode 106, thewiring electrode 108, and the piezoelectric film 111.

The ink-repellent film 116 covers the surface 113 a of the protectivefilm 113. The ink-repellent film 116 is made of a silicon-seriesliquid-repellent material having liquid repellency. Note that theink-repellent film 116 may be made of another material such as afluorinated organic material. The thickness of the ink-repellent film116 is, for example, 1 μm. The ink-repellent film 116 does not cover butexposes the protective film 113 around the shared electrode terminalunit and the wiring electrode terminal unit.

As shown in FIG. 4, the ink flow path structure 300 includes the fixingsurface 301, the ink supply flow paths 304, and the ink recovery flowpaths 305. The ink flow path structure 300 is made of, for example,stainless steel, and has a rectangular plate shape. The thickness of theink flow path structure 300 is, for example, 4 mm. The fixing surface301 of the ink flow path structure 300 is bonded to the second endsurface 200 b of the pressure cell structure 200 with, for example,epoxy-based adhesive.

The ink flow path structure 300 may not be made of stainless steel. Theink flow path structure 300 may be made of any other material such asceramics, resin, and metal (alloy) as long as the pressure is notincreased to eject the ink, in consideration of the difference betweenthe expansion coefficient of the ink flow path structure 300 and theexpansion coefficient of the nozzle plate 100. Ceramics such as, forexample, nitride and oxide such as alumina ceramics, zirconia, siliconcarbide, silicon nitride, and barium titanate is used. Resin such as,for example, a plastic material such as ABS, polyacetal, polyamide,polycarbonate, and polyethersulfone is used. Metal such as, for example,aluminum and titanium is used.

An ink inlet port (not shown) is arranged at one end of the ink flowpath structure 300. The ink inlet port is connected to the ink tank 501via a path such as a tube, for example. For example, the pressurecontrol pump 504 supplies the ink stored in the ink tank 501 to the inkinlet port.

An ink recovery port (not shown) is arranged at the other end of the inkflow path structure 300. The ink inlet port and the ink recovery portmay not be arranged at both the ends of the ink flow path structure 300.For example, both the ink inlet port and the ink recovery port may bearranged at one end of the ink flow path structure 300, or may bearranged at the center of the ink flow path structure 300.

The ink recovery port is connected to the ink tank 502 via a path suchas a tube, for example. For example, the pressure control pump 503recovers the ink flowing into the ink recovery port, in the ink tank502.

As shown in FIG. 5, the ink supply flow paths 304 are grooves on thefixing surface 301. The ink supply flow paths 304 extend in parallel ina predetermined direction. The depth of the ink supply flow path 304 is,for example, 1 mm. One end of the ink supply flow path 304 is connectedto the ink inlet port. According to this structure, ink, which issupplied from the ink tank 501 to the ink inlet port, flows into the inksupply flow path 304.

The ink recovery flow paths 305 are grooves on the fixing surface 301.As shown in FIG. 5, each ink recovery flow path 305 is arranged betweeneach two ink supply flow paths 304. The ink recovery flow paths 305extend in parallel with the ink supply flow paths 304 in thepredetermined direction. The depth of the ink recovery flow path 305 is,for example, 1 mm. One end of the ink recovery flow path 305 isconnected to the ink recovery port. According to this structure, ink,which is flowed into the ink recovery flow path 305, is recovered in theink tank 502 via the ink recovery port.

In this embodiment, as shown in FIG. 3, FIG. 4, and FIG. 6, the pressurecell structure 200 includes the flow control paths 202, 203 and theslits 204, 205. The flow control paths 202, 203 and the slits 204, 205control ink flowing into the pressure cell 201. The flow control path202 and the slit 204 are at one side of the pressure cell 201, and theflow control path 203 and the slit 205 are at the other side of thepressure cell 201, the pressure cell 201 being interposed therebetween.Each of the flow control paths 202, 203 corresponds to each pressurecell 201, is an approximately rectangular long through hole, and isformed from the first end surface 200 a of the pressure cell structure200 to the second end surface 200 b thereof in the thickness directionof the pressure cell structure 200.

The slit 204 is formed between the flow control path 202 at one side ofthe pressure cell 201 and the pressure cell 201. Similarly, the slit 205is formed between the flow control path 203 at the other side of thepressure cell 201 and the pressure cell 201. Each of the slits 204, 205is a narrow groove, and is formed from the first end surface 200 a ofthe pressure cell structure 200 to the second end surface 200 b thereofin the thickness direction of the pressure cell structure 200. The slit204 is in communication with the pressure cell 201 and the flow controlpath 202, the slit 205 is in communication with the pressure cell 201and the flow control path 203, and the width of each slit 204, 205 issmaller than the width of the pressure cell 201. In this case, the widthof each slit 204, 205 is, for example, the width 204 w, 205 w of FIG. 6.The width of the pressure cell 201 is the width 201 w (diameter ofpressure cell) of FIG. 6. In other words, the width 204 w, 205 w is thewidth of each slit 204, 205 in the direction slightly inclined from Xdirection to Y direction. In other words, similarly, the width 201 w isthe width of the pressure cell 201 in the direction inclined. Note that,in FIG. 3, the nozzles 101 are arrayed in the direction inclined.Further, in FIG. 5, the ink supply flow paths 304 and the ink recoveryflow paths 305 are arrayed in the direction inclined. Note that,preferably, the width of each slit 204, 205 is the same as the width ofthe nozzle 101 (diameter of nozzle).

As shown in FIG. 4, the ink flow path structure 300 includes the firstconnection ports 307 and the second connection ports 308. The firstconnection ports 307 are in communication with the ink supply flow paths304. The second connection ports 308 are in communication with the inkrecovery flow paths 305. The first and second connection ports 307, 308are formed by bonding the pressure cell structure 200 and the ink flowpath structure 300. As shown in FIG. 4, the end of the flow control path202 and the end of the ink supply flow path 304 form the firstconnection port 307. Further, the end of the flow control path 203 andthe end of the ink recovery flow path 305 form the second connectionport 308. The end of the ink supply flow path 304, which forms the firstconnection port 307, is in parallel with the end of the ink recoveryflow path 305, which forms the second connection port 308.

Further, the first connection ports 307 are in communication with theflow control paths 202, and the second connection ports 308 are incommunication with the flow control paths 203. Here, each firstconnection port 307 is in communication with each flow control path 202of the pressure cell structure 200. Similarly, each second connectionport 308 is in communication with each flow control path 203 of thepressure cell structure 200.

With this structure, ink flows into the ink supply flow path 304, passesthrough the first connection port 307, and flows into the flow controlpath 202 of the pressure cell structure 200. Then, the ink flows fromthe flow control path 202, passes through the slit 204, and flows intothe pressure cell 201. Then, the ink in the pressure cell 201 passesthrough the slit 205, flows into the flow control path 203 side, passesthrough the second connection port 308, and flows into the ink recoveryflow path 305.

Next, how the piezoelectric film 111 of the actuator 102 works will bedescribed further. As described above, the piezoelectric film 111expands or contracts in the film thickness direction (Z direction), andcontracts or expands in the direction (in-plane direction, X, Ydirections) perpendicular to the film thickness direction.

In the following description, expansion and contraction of thepiezoelectric film 111 only in the in-plane direction will be described,and expansion of the piezoelectric film 111 in the film thicknessdirection will not be described.

When the piezoelectric film 111 contracts in the in-plane direction (X,Y directions), the actuator 102 including the piezoelectric film 111deforms (bends) in the direction apart from the pressure cell 201. Inother words, the actuator 102 deforms (bends) in the direction in whichthe volume of the pressure cell 201 is increased. As a result, when theactuator 102 bends as described above, the vibration plate 109, which isconnected to the piezoelectric film 111, bends in the direction in whichthe volume of the pressure cell 201 is increased. When the vibrationplate 109 bends in the direction in which the volume of the pressurecell 201 is increased, negative pressure is applied to the ink retainedin the pressure cell 201. When the negative pressure is applied, the inkflows from the ink flow path structure 300 into the flow control path202 of the pressure cell structure 200. Further, the ink in the flowcontrol path 202 passes through the slit 204, and is supplied to thepressure cell 201.

When the piezoelectric film 111 expands in the in-plane direction, theactuator 102 deforms (bends) in the direction toward the pressure cell201. In other words, the actuator 102 bends in the direction in whichthe volume of the pressure cell 201 is decreased. As a result, when theactuator 102 bends as described above, the vibration plate 109, which isconnected to the piezoelectric film 111, bends in the direction in whichthe volume of the pressure cell 201 is decreased. When the vibrationplate 109 bends in the direction in which the volume of the pressurecell 201 is decreased, positive pressure is applied to the ink retainedin the pressure cell 201. When the positive pressure is applied, inkdrops are ejected from the nozzle 101. The ink is ejected in Zdirection. When the volume of the pressure cell 201 is decreased, partof the vibration plate 109 near the nozzle 101 deforms in the directionof the ejection of the ink, because the piezoelectric film 111 deforms(expands in in-plane direction). In other words, the actuator 102 worksin the bending mode to eject ink.

The inkjet head 21 performs printing (forms images) as follows, forexample. Ink is supplied from the ink tank 501 to the ink inlet port ofthe ink flow path structure 300.

The ink passes through the ink supply flow path 304 and the firstconnection port 307, and flows into the flow control path 202 of thepressure cell structure 200. Further, the ink in the flow control path202 passes through the slit 204, and is supplied to the pressure cell201. The ink supplied to the pressure cell 201 is supplied to thecorresponding nozzle 101, and forms a meniscus on the nozzle 101. In theinkjet printer 1, the pressure control pumps 503, 504 control thepressure of the ink supplied from the ink inlet port to obtain anappropriate negative pressure, and the ink is thereby kept in the nozzle101 such that the ink may not leak from the nozzle 101.

For example, in response to an operation from a user, a printinstruction signal is input in a controller (not shown). In response tothe printing instruction, the controller outputs the signal to theactuator 102 via the wiring electrode 108. In other words, thecontroller applies a drive voltage to the electrode part 108 a of thewiring electrode 108. As a result, an electric field in the filmthickness direction (Z direction) is applied to the piezoelectric film111, and the piezoelectric film 111 expands and contracts as describedabove. Then the actuator 102 bends as described above.

The actuator 102 is sandwiched between the vibration plate 109 and theprotective film 113. With this structure, when the piezoelectric film111 expands in X, Y directions and the actuator 102 bends, a force isapplied to the vibration plate 109, and the vibration plate 109 deformsin a concave shape in the direction toward the pressure cell 201 side.To the contrary, a force is applied to the protective film 113, and theprotective film 113 deforms in a convex shape in the direction towardthe pressure cell 201 side.

When the piezoelectric film 111 contracts in X, Y directions and theactuator 102 bends, a force is applied to the vibration plate 109, andthe vibration plate 109 deforms in a convex shape in the directiontoward the pressure cell 201. To the contrary, a force is applied to theprotective film 113, and the protective film 113 deforms in a concaveshape in the direction toward the pressure cell 201.

The Young's modulus of a polyimide film, which forms the protective film113, is smaller than the Young's modulus of an SiO₂ film, which formsthe vibration plate 109. Because of this, when the same amount of forceis applied to the protective film 113 and the vibration plate 109, theprotective film 113 deforms larger than the vibration plate 109. Whenthe piezoelectric film 111 of the actuator 102 expands in X, Ydirections, the nozzle plate 100 deforms in a convex shape in thedirection toward the pressure cell 201 side. As a result, the volume ofthe pressure cell 201 is decreased (because the deformation amount ofthe protective film 113 in a convex shape in the direction toward thepressure cell 201 is larger).

To the contrary, when the piezoelectric film 111 of the actuator 102contracts in X, Y directions, the nozzle plate 100 deforms in a concaveshape in the direction toward the pressure cell 201 side. As a result,the volume of the pressure cell 201 is increased (because thedeformation amount of the protective film 113 in a concave shape in thedirection toward the pressure cell 201 is larger).

When the vibration plate 109 deforms and the volume of the pressure cell201 is changed, the pressure of the ink in the pressure cell 201 ischanged. When the pressure is changed, the ink in the nozzle 101 isejected. At this time, the slits 204, 205 control the ink pressurized inthe pressure cell 201 such that the ink may not flow into the flowcontrol paths 202, 203. The slits 204, 205 thereby prevent the volumeand the ejection speed of the ink ejected from the nozzle 101 from beingdecreased.

The larger the difference between the Young's modulus of the vibrationplate 109 and the Young's modulus of the protective film 113, the largerthe deformation amount of the vibration plate 109 when a predeterminedvoltage is applied to the actuator 102. Because of this, the larger thedifference between the Young's modulus of the vibration plate 109 andthe Young's modulus of the protective film 113, the lower the voltage ofthe ink ejection.

If the film thickness and the Young's modulus of the vibration plate 109are the same as those of the protective film 113, when voltage isapplied to the actuator 102, the same amount of forces are applied tothe vibration plate 109 and the protective film 113, and the plate 109and the protective film 113 thereby deform in the opposite directions bythe same amount. As a result, the vibration plate 109 does not deform.

Note that, as described above, not only the Young's modulus of thematerial but also the thickness of the plate affects the deformationamount of the plate member. In view of this, in order to make thedeformation amount of the vibration plate 109 and the deformation amountof the protective film 113 different, not only the Young's moduli of thematerials but also the thicknesses of films are considered. Even if theYoung's modulus of the material of the vibration plate 109 is the sameas that of the protective film 113, if the thickness of one film isdifferent from that of the other, it is possible to eject ink, whichrequires the higher drive voltage, though.

The ink outlet port is an opening at the end of the ink recovery flowpath 305. The ink outlet port is connected to the ink tank 502 via atube, for example. The ink, which is not ejected from the nozzle 101,flows from the pressure cell 201, passes through the slit 205, the flowcontrol path 203, the second connection port 308, the ink recovery flowpath 305, and the ink outlet port, and is discharged to the ink tank502. As described above, the ink circulates in the ink tank 501, the inksupply flow path 304, the flow control path 202, the pressure cells 201,the flow control path 203, the ink recovery flow path 305 the ink tank502, and the ink circulation pump 505. Because the ink circulates, thetemperature of the inkjet head 21 and the temperature of the ink arekept constant, and the quality of the ink is less changed affected byheat, for example.

Next, an example of a method of manufacturing the inkjet head 21 will bedescribed. First, before forming the pressure cells 201, the flowcontrol paths 202, 203, and the slits 204, 205, an SiO₂ film is formedas the vibration plate 109 on the entire area of the first end surface200 a of the pressure cell structure 200 (silicon wafer). The SiO₂ filmis formed by a thermally-oxidized film-forming method, for example. Notethat the SiO₂ film may be formed by using another method such as a CVDmethod.

A silicon wafer, from which the pressure cell structure 200 is formed,is one large circular plate. The pressure cell structures 200 are cutout from the silicon wafer later. Alternatively, one pressure cellstructure 200 may be one rectangular silicon wafer.

The silicon wafer is repeatedly heated and thin films are formed whenthe inkjet head 21 is manufactured. In view of this, the silicon waferis heat-resistant, complies with SEMI (Semiconductor Equipment andMaterials International) standard, and is mirror-polished and smoothed.

Next, a metal film as the shared electrode 106 is formed on the secondsurface 109 b of the vibration plate 109. First, Ti and Pt aresputtered, and Ti and Pt films are formed in order. The film thicknessof Ti is, for example, 0.45 μm. The film thickness of Pt is, forexample, 0.05 μm. Note that the metal films may be formed by anothermethod such as vapor deposition and metal plating.

After the metal film is formed, the shared electrode 106 is formed bypatterning. An etching mask is formed on the electrode film, part of theelectrode material uncovered by the etching mask is etched and removed,and the shared electrode 106 is thereby patterned.

Because the nozzle 101 is formed at the center of each electrode part106 a of the shared electrode 106, a portion without the electrode filmis formed, the portion and the electrode part 106 a being concentric,the center of the portion and the center of the electrode part 106 abeing the same. After the shared electrode 106 is patterned, thevibration plate 109 is exposed except for the electrode part 106 a,wiring part, and the shared electrode terminal unit of the sharedelectrode 106.

Next, the piezoelectric film 111 is formed on the shared electrode 106.The piezoelectric film 111 is formed by, for example, an RF magnetronsputtering method at the substrate temperature 350° C. After thepiezoelectric film 111 is formed, the piezoelectric film 111 is heatedat 500° C. for 3 hours in order to apply piezoelectricity. As a result,the piezoelectric film 111 obtains good piezoelectricity. Thepiezoelectric film 111 may be formed by another method such as, forexample, CVD (chemical vapor deposition), a sol-gel method, an AD method(aerosol deposition method), and a hydrothermal synthesis method. Afterthe piezoelectric film 111 is formed, it is etched and patterned.

Because the nozzle 101 is formed at the center of the piezoelectric film111, a portion without the piezoelectric film is formed, the portion andthe piezoelectric film 111 being concentric. The vibration plate 109 isexposed except for the piezoelectric film 111. The piezoelectric film111 covers the electrode part 106 a of the shared electrode 106.

Next, the insulation film 112 is formed on part of the piezoelectricfilm 111 and part of the shared electrode 106. The insulation film 112is formed by the CVD method, which realizes a good insulation propertiesat a low temperature. The insulation film 112 is formed and thenpatterned. The insulation film 112 covers only part of the piezoelectricfilm 111 in order to reduce troubles resulting from non-uniformpatterning. The insulation film 112 covers the piezoelectric film 111 soas not to reduce the deformation amount of the piezoelectric film 111.

Next, a metal film is formed on the vibration plate 109, thepiezoelectric film 111, and the insulation film 112 to form the wiringelectrodes 108. The metal film is formed by a sputtering method. Themetal film may be formed by another method such as a vacuum vapordeposition and a metal plating.

The metal film is patterned, and the wiring electrodes 108 are therebyformed. An etching mask is formed on the electrode film, part of theelectrode material uncovered by the etching mask is etched and removed,and the wiring electrodes 108 are thereby patterned.

Because the nozzle 101 is formed at the center of the electrode part 108a of the wiring electrode 108, a portion without the electrode film isformed, the portion and the electrode part 108 a of the wiring electrode108 being concentric, the center of the portion and the center of theelectrode part 108 a being the same. The electrode part 108 a of thewiring electrode 108 covers the piezoelectric film 111.

Next, the SiO₂ film of the vibration plate 109 is patterned, and part ofthe nozzle 101 is thereby formed. An etching mask is formed on the SiO₂film, part of the SiO₂ film uncovered by the etching mask is etched andremoved, and part of the nozzle 101 is thereby patterned.

The etching mask is formed as follows. The vibration plate 109 is coatedwith a photosensitive resist, then prebaked, exposed with light where itis covered with a mask on which a desired pattern is formed, developed,and postbaked.

Next, the protective film 113 is formed on the second surface 109 b ofthe vibration plate 109 by a spin coating method. The protective film113 may be formed by another method such as, for example, CVD, vacuumvapor deposition, and metal plating.

Next, the protective film 113 is patterned, and the nozzles 101 arethereby formed. Holes are formed through the protective film 113, theholes being in communication with part of the nozzles 101 through thevibration plate 109, and the nozzles 101 are thereby formed. Further, bypatterning the protective film 113, the shared electrode terminal unitand the wiring electrode terminal unit are exposed.

For example, polyimide precursor-containing solution is spin coated toform a film. The solution is baked for thermal polymerization, removed,and thereby burned and formed. After that, an etching mask is formed onthe polyimide film, part of the polyimide film uncovered by the etchingmask is etched and removed, and the polyimide film is thereby patterned.The etching mask is formed as follows. The polyimide film is coated witha photosensitive resist, then prebaked, exposed with light where it iscovered with a mask on which a desired pattern is formed, developed, andpostbaked.

Next, a cover tape is adhered to the protective film 113. The cover tapeis, for example, a back-side protective tape for chemical mechanicalpolishing (CMP) for a silicon wafer. The pressure cell structure 200with the cover tape is turned upside down, and the pressure cells 201,the flow control paths 202, 203, and the slits 204, 205 are formedthrough the pressure cell structure 200. The pressure cells 201, theflow control paths 202, 203, and the slits 204, 205 are formed bypatterning.

An etching mask is formed on the pressure cell structure 200 being asilicon wafer, and part of the silicon wafer uncovered by the etchingmask is removed by using a so-called vertical deep dry etching dedicatedto silicon substrates. As a result, the pressure cells 201, the flowcontrol paths 202, 203, and the slits 204, 205 are formed.

SF6 gas is used for this etching. The SiO₂ film of the vibration plate109 and the polyimide film of the protective film 113 are not etchedwhen SF6 gas is used. Because of this, the silicon wafer, which formsthe pressure cells 201, is dry etched, but the vibration plate 109 andthe other members are not dry etched.

Note that, instead of that etching, any one of various methods may beused such as wet etching in which chemical solution is used and dryetching in which plasma is used. The etching methods and the etchingconditions may be changed depending on the materials of the insulationfilm, the electrode film, the piezoelectric film, and the like. Afterthe etching process, in which each photosensitive resist film is used,is finished, the remaining photosensitive resist film is removed byusing solution.

Next, the ink flow path structure 300 is bonded to the pressure cellstructure 200. By bonding the ink flow path structure 300 to thepressure cell structure 200, the first and second connection ports 307,308 are formed.

Next, a cover tape is adhered to the protective film 113, and the covertape thereby covers the shared electrode terminal unit and the wiringelectrode terminal unit. The cover tape is made of resin, and the covertape can thereby be removed from the protective film 113 easily. Thanksto the cover tape, dusts and the ink-repellent film 116 (describedlater) less attach to the shared electrode terminal unit and the wiringelectrode terminal unit.

Next, the ink-repellent film 116 is formed on the protective film 113. Aliquid ink-repellent film material is spin coated on the protective film113, and the ink-repellent film 116 is thereby formed. At this time,positive pressure air injected into the ink inlet port and the inkrecovery port. As a result, positive pressure air is discharged from thenozzle 101 in communication with the ink supply flow path 304. When theliquid ink-repellent film material is coated on the protective film 113in this situation, the ink-repellent film material less attaches to theinner wall of the nozzle 101. After the ink-repellent film 116 isformed, the cover tape is peeled from the protective film 113.

The inkjet head 21 is manufactured as the result of those steps. Theinkjet head 21 is mounted in the inkjet printer 1. A controller isconnected to the wiring electrode terminal unit via, for example, aflexible cable. Further, the ink inlet port and the ink recovery port ofthe ink flow path structure 300 are connected to the ink tanks 501, 502.

According to the inkjet printer 1 of the first embodiment, the pressurecell structure 200 includes the flow control paths 202, 203 and theslits 204, 205, which control flow of ink in each pressure cell 201. Theflow control path 202 and the slit 204 are at one side of the pressurecell 201, and the flow control path 203 and the slit 205 are at theother side of the pressure cell 201, the pressure cell 201 beingtherebetween. According to this structure, when the inkjet printer 1operates, ink flows into the ink supply flow path 304, passes throughthe first connection port 307, and flows into the flow control path 202of the pressure cell structure 200. Further, the ink flows from the flowcontrol path 202, passes through the slit 204, and flows into thepressure cell 201. Then, the ink in the pressure cell 201 passes throughthe slit 205, flows into the flow control path 203 side, passes throughthe second connection port 308, and flows into the ink recovery flowpath 305. As a result, the ink in the pressure cell 201 is constantlyrefilled. As a result, even if air bubbles are generated in the pressurecell 201, the air bubbles are discharged from the second connection port308 together with ink. So it is possible to prevent poor ink ejectionfrom occurring due to air bubbles. Further, when the actuator 102pressurizes ink in the pressure cell 201 and the ink is ejected from thenozzle 101, the slit 204 controls the pressurized ink flowing from thepressure cell 201 to the flow control path 202, and the slit 205controls the pressurized ink flowing from the pressure cell 201 to theflow control path 203. As a result, the ink pushed out of the pressurecell 201 by the actuator 102 is ejected from the nozzle 101 effectively.

Further, because the ink is not kept in the pressure cell 201 but flows,the ink near the nozzle 101 is refilled constantly. As a result, thefollowing situation is prevented from occurring; ink solvent in thenozzle 101 dries, the ink pigments aggregate, and the nozzle 101 isclogged with the pigment aggregates.

As described above, it is possible to prevent poor ink ejection fromoccurring due to air bubbles and aggregated pigments. So it is notnecessary to refill the pressure cell 201 with ink, for example, tomaintain the pressure cell 201. As a result, the operational efficiencyof the inkjet printer 1 is increased, and maintenance costs may bedecreased.

Further, because fresh ink is constantly supplied to the pressure cell201, it is possible to keep the temperature of the ink in the pressurecell 201 constant. In other words, heat is generated when the nozzleplate 100 deforms, and the inkjet head 21 prevents increase of thetemperature of the ink due to that heat from occurring. As a result, itis possible to prevent change of properties of the ink due to change ofthe temperature from occurring.

Second Embodiment

FIG. 7 shows a second embodiment. This embodiment shows a modificationin which the structure of the inkjet head 21 of the first embodiment(see FIG. 1 to FIG. 6) is modified as follows.

In short, the inkjet head 21 of this embodiment includes the inkinlet-side flow control path 401. In the first embodiment, as shown inFIG. 3, each of the flow control paths 202 is a path segmented for eachcorresponding pressure cell 201. To the contrary, the ink inlet-sideflow control path 401 is a common path including the flow control paths202 of the first embodiment in communication with each other. The slit403 is formed between the ink inlet-side flow control path 401 and eachpressure cell 201. Further, the ink inlet-side flow control path 401 isin communication with each pressure cell 201 via each slit 403.

Further, the inkjet head 21 of this embodiment includes the inkoutlet-side flow control path 402. In the first embodiment, as shown inFIG. 3, each of the flow control paths 203 is a path segmented for eachcorresponding pressure cell 201. To the contrary, the ink outlet-sideflow control path 402 is a common path including the flow control paths203 of the first embodiment in communication with each other. The slit404 is formed between the ink outlet-side flow control path 402 and eachpressure cell 201. Further, the ink outlet-side flow control path 402 isin communication with each pressure cell 201 via each slit 404.

As described above, the inkjet head 21 of this embodiment includes theink inlet-side flow control path 401, which includes the ink inlet-sideflow control paths 202 for the pressure cells 201 in communication witheach other, and the ink outlet-side flow control path 402, whichincludes the ink outlet-side flow control paths 203 for the pressurecells 201 in communication with each other. With this structure, thestructure of the pressure cell structure 200 is made simple, and thepressure cell structure 200 is manufactured easily.

According to the inkjet head and the inkjet recording apparatus of theembodiments, it is possible to prevent air bubbles from remaining in thepressure cell, and to prevent poor ink ejection from occurring.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of this embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. An inkjet head, comprising: a pressure cellstructure having a first end surface and a second end surface; a nozzleplate on a side of the first end surface of the pressure cell structure;and an ink flow path structure positioned on the second end surface ofthe pressure cell structure, wherein the pressure cell structureincludes: pressure cells that retain ink, each of the pressure cellsbeing formed in a thickness direction of the pressure cell structurefrom the first end surface of the pressure cell structure to the secondend surface of the pressure cell structure, flow control paths, each ofwhich is in fluid communication with one of the pressure cells, each ofthe pressure cells being interposed between two of the flow controlpaths, each of the flow control paths being formed in the thicknessdirection of the pressure cell structure, and slits, each of which is influid communication with one of the pressure cells through one of theflow control paths, each of the slits having a width smaller than awidth of each of the pressure cells, the nozzle plate includes:actuators formed on the first end surface of the pressure cellstructure, each of the actuators covering one of the pressure cells, theactuators deforming in the thickness direction of the pressure cellstructure depending on a drive voltage, and nozzles, each of the nozzlescorresponding to one of the actuators, each of the nozzles being influid communication with one of the pressure cells, each of the nozzlesejecting the ink retained in one of the pressure cells in response tothe corresponding actuator deforming, and the ink flow path structureincludes: ink flow paths in fluid communication with the pressure cellsvia the flow control paths and the slits.
 2. The inkjet head accordingto claim 1, wherein the ink flow paths of the ink flow path structureinclude: an ink supply flow path in fluid communication with one of thetwo interposing flow control paths at one side of the pressure cell, andan ink recovery flow path in fluid communication with another of the twointerposing flow control paths at the other side of the pressure cell.3. The inkjet head according to claim 2, wherein the ink flow pathstructure includes: a first connection port in fluid communication withthe flow control path at one side of the pressure cell, and a secondconnection port in fluid communication with the flow control path at theother side of the pressure cell, wherein the ink flows into the flowcontrol path at the one side of the pressure cell from the ink supplyflow path via the first connection port, and the ink flows into the inkrecovery flow path from the flow control path at the other side of thepressure cell via the second connection port.
 4. The inkjet headaccording to claim 1, wherein the flow control paths include pathsegments for the pressure cells.
 5. The inkjet head according to claim1, wherein each slit has a width the same as a width of a correspondingnozzle.
 6. The inkjet head according to claim 1, wherein: the flowcontrol path at the one side of the corresponding pressure cell is acommon path in fluid communication with each other side of the pressurecell, and the flow control path at the other side of the correspondingpressure cell is a common path in fluid communication with thecorresponding flow control path of adjacent pressure cells.
 7. An inkjetrecording apparatus, comprising: a conveyer apparatus that conveysrecording paper; and an inkjet head that ejects ink onto the recordingpaper conveyed by the conveyer apparatus to form an image, wherein: theinkjet head includes: a pressure cell structure having a first endsurface and a second end surface, a nozzle plate on a side of the firstend of the pressure cell structure, and an ink flow path structurepositioned on the second end surface of the pressure cells structure,the pressure cell structure including: pressure cells that retain ink,each of the pressure cells being formed in a thickness direction of thepressure cell structure from the first end surface of the pressure cellstructure to the second end surface of the pressure cells structure,flow control paths, each of which is in fluid communication with one ofthe pressure cells, each of the pressure cells being interposed betweentwo of the flow control paths, the flow control paths being formed inthe thickness direction of the pressure cell structure, and slits, eachof which is in fluid communication with one of the pressure cells andthrough one of the flow control paths, each of the slits having a widthsmaller than a width of the pressure cells, the nozzle plate includes:actuators formed on the first end surface of the pressure cellstructure, the actuators covering one of the pressure cells, theactuators deforming in the thickness direction of the pressure cellstructure depending on a drive voltage, and nozzles, each of the nozzlescorresponding to one of the actuators, each of the nozzles being influid communication with one of the pressure cells, the nozzles ejectingthe ink retained in one of the pressure cells in response to thecorresponding actuator deforming, and the ink flow path structureincludes: ink flow paths in fluid communication with the pressure cellsvia the flow control paths and slits.
 8. The inkjet recording apparatusaccording to claim 7, wherein each slit has a width the same as a widthof a corresponding nozzle.
 9. The inkjet recording apparatus accordingto claim 7, wherein, for a plurality of the pressure cells: one of thetwo flow control paths at one side of each of the plurality of pressurecells is a common path in fluid communication with each other, andanother of the two flow control paths at the other side of the pluralityof pressure cells is a common path in fluid communication with eachother.
 10. An inkjet head, comprising: a nozzle plate having a pluralityof nozzles configured to eject ink in a first direction; a plurality ofactuators arranged on the nozzle plate, each of which corresponding withone of the nozzles, the plurality of actuators configured to deformbased on a drive voltage; a pressure chamber structure having a firstsurface on which the nozzle plate is formed and a second surfaceparallel to the first surface; a pressure chamber formed between thefirst surface and the second surface of the pressure chamber structureand in fluid communication with one of the nozzles; a first slit formedin a sidewall of the pressure chamber, extending from the second surfaceof the pressure chamber structure and in fluid communication with thepressure chamber, a width of the first slit in a second directionperpendicular to the first direction being smaller than a width of thepressure chamber; a second slit formed in the sidewall of the pressurechamber structure at a different position from the first slit, extendingfrom the second surface of the pressure chamber and in fluidcommunication with the pressure chamber, a width of the second slit in athird direction perpendicular to the first direction being smaller thanthe width of the pressure chamber; a first flow control path in fluidcommunication with the first slit; a second flow control path in fluidcommunication with the second slit; and an ink flow path structuredisposed on the second surface of the pressure chamber structure, theink flow path structure including a first ink flow path in fluidcommunication with the first flow control path and a second ink flowpath in fluid communication with the second flow control path.
 11. Theinkjet head according to claim 10, wherein: a width of the first flowcontrol path in the second direction is greater than the width of thefirst slit, and a width of the second flow control path in the thirddirection is greater than the width of the second slit.
 12. The inkjethead according to claim 11, wherein: the pressure chamber is a circularhole, and the width of the pressure chamber is a diameter.
 13. Theinkjet head according to claim 12, wherein: the second slit ispositioned at an opposite side of the pressure chamber to the firstslit, and the second direction and the third direction are samedirection.
 14. The inkjet head according to claim 13, wherein: the firstslit and the second slit each extend from the second surface of thepressure chamber structure to the first surface.
 15. The inkjet headaccording to claim 14, wherein: the first flow control path and thesecond flow control path each include a portion that extends from thesecond surface of the pressure chamber structure to the first surface ofthe pressure chamber structure.